What is climate?

When people talk about climate and the environment, they're referring to gradual shifts in temperatures and weather patterns over time. The time frame is usually decades or centuries, not the hourly changes in the daily weather forecast.

That shift can be natural, linked to solar activity or volcanic eruptions — like that of Indonesia's Mount Tambora in April 1815. The ash and gases from that massive explosion blocked out sunlight, reducing the average global temperature by up to 3 degrees Celsius (5.4 Fahrenheit). Heavy snow and frost struck parts of Western Europe and North America in June, July and August of 1816, the infamous "year without a summer."

But most of the recent changes to the global climate have been driven by people and how we live. Over the last 200 years, greenhouse gas emissions — primarily carbon dioxide and methane — from transportation, agriculture, heating and other human activities have built up in the atmosphere, trapping heat and gradually warming the planet.

Climate scientists have linked these growing emissions, largely from fossil fuels, to increasing temperatures and more extreme weather conditions around the world. Recent analyses from agencies like the World Meteorological Organization and the EU's Copernicus Climate Change Service confirmed that 2023 was the hottest year on record, by a wide margin.

How does climate change affect the weather?

World Weather Attribution, a group of scientific organizations that uses real-world data and climate models to link climate change and extreme weather events around the world, investigated more than a dozen disasters in 2023. Using this scientific evidence, it explained how fossil fuel emissions — which hit a record high in 2023 — are making storms, droughts, wildfires and heat waves deadlier and more destructive.

WWA found, for example, that the hot, dry conditions that fueled some of Canada's record wildfire season in 2023 — which wiped out more than 18 million hectares, an area about the size of Syria — were at least twice more likely in a warming world. And it revealed that climate change increased the intensity of heavy rainfall in Libya in September by up to 50%, thus partly causing the catastrophic floods that killed more than 3,400 people.

The Earth is warming, so why is it so cold?

Despite higher temperatures, parts of the world still regularly shiver through bone-chilling cold snaps. And that, too, is part of climate change.

Extreme cold weather in Europe and North America is made more likely by the collapse of the polar vortex, the cold winds that rage around the North Pole, and the weakening jet stream, both of which are influenced by the warming Arctic. If the jet stream — the band of strong winds that circle the globe — begins to waver, the warm air from the tropics and the frigid polar winds can shift, causing unseasonably warm weather, or icy blizzards, thousands of kilometers away.

Why does climate change matter?

On the world's current trajectory, UN calculations show greenhouse gas emissions are expected to push temperatures to as much as 2.9 degrees Celsius (5.2 Fahrenheit) above preindustrial levels by 2100. We've already seen an increase of 1.4 degrees Celsius, and the devastating weather consequences.

And even if you live in a part of the world where the effects of climate change aren't as extreme, you'll still be affected. Increased migration, food prices and general global instability all go hand in hand with a warming planet.

Edited by: Sarah Steffen